Battery cell for electric vehicle battery pack

ABSTRACT

A battery cell of a battery pack to power an electric vehicle can include a housing to at least partially enclose an electrode assembly is provided. The battery cell can include a vent plate coupled with the housing via a glass weld at a lateral end of the battery cell. The vent plate can include a scoring pattern to cause the vent plate to rupture in response to a threshold pressure. A first end of a polymer tab can be electrically coupled with the vent plate at an area within a scored region defined by the scoring pattern. A second end of the polymer tab can be electrically coupled with an electrode assembly. The polymer tab can melt in response to either a threshold temperature or a threshold current within the battery cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 U.S.Provisional Patent Application 62/646,987, filed Mar. 23, 2018 andtitled “BATTERY CELL FOR ELECTRIC VEHICLE BATTERY PACK,” which isincorporated herein by reference in its entirety.

BACKGROUND

Electric vehicles such as automobiles can include on-board battery cellsor battery packs to power the electric vehicles. Batteries canexperience a condition known as thermal runaway under some operatingconditions or environmental conditions.

SUMMARY

At least one aspect of this disclosure is directed to a battery cell ofa battery pack to power an electric vehicle. The battery cell caninclude a housing to at least partially enclose an electrode assembly.The housing can define a side surface of the battery cell. The batterycell can include a first polarity terminal including at least a portionof the housing. The battery cell can include a vent plate coupled withthe housing via a glass weld at a lateral end of the battery cell toelectrically insulate the vent plate from the housing. The vent platecan include a scoring pattern to cause the vent plate to rupture inresponse to a threshold pressure within the battery cell. The scoringpattern can define a scored region on the vent plate. The battery cellcan include a second polarity terminal including at least a portion ofthe vent plate. The battery cell can include an electrically conductivepolymer tab to electrically connect the electrode assembly to the secondpolarity terminal. The polymer tab can have a first end and a secondend. The first end of the polymer tab can be electrically coupled withthe vent plate at an area within the scored region defined by thescoring pattern on the vent plate. The second end of the polymer tab canbe electrically coupled with the electrode assembly. The polymer tab canmelt in response to either a threshold temperature or a thresholdcurrent within the battery cell.

At least one aspect of this disclosure is directed to a method ofproviding battery cells for battery packs of electric vehicles. Themethod can include forming a housing for a battery cell of a batterypack having a plurality of battery cells. The housing can define a sidesurface of the battery cell. The housing can form at least a portion ofa first polarity terminal of the battery cell. The method can includeproviding an electrode assembly within the housing. The method caninclude etching a scoring pattern into a vent plate to cause the ventplate to rupture when exposed to a pressure exceeding a thresholdpressure. the scoring pattern can define a scored region on the ventplate. The vent plate can form at least a portion of a second polarityterminal of the battery cell. The method can include electricallycoupling a first end of an electrically conductive polymer tab with thevent plate at an area within the scored region defined by the scoringpattern on the vent plate. The polymer tab can melt when exposed toeither a threshold temperature or a threshold current. The method caninclude electrically coupling a second end of the polymer tab, oppositethe first end of the polymer tab, with the electrode assembly. Themethod can also include coupling the vent plate with housing via a glassweld to form a seal around the electrode assembly and the polymer tab.

At least one aspect of this disclosure is directed to an electricvehicle. The electric vehicle can include a battery pack installed inthe electric vehicle. A battery cell can be installed in the batterypack. The battery cell can include a housing to at least partiallyenclose an electrode assembly. The housing can define a side surface ofthe battery cell. The battery cell can include a first polarity terminalincluding at least a portion of the housing. The battery cell caninclude a vent plate coupled with the housing via a glass weld at alateral end of the battery cell to electrically insulate the vent platefrom the housing. The vent plate can include a scoring pattern to causethe vent plate to rupture in response to a threshold pressure within thebattery cell. The scoring pattern can define a scored region on the ventplate. The battery cell can include a second polarity terminal includingat least a portion of the vent plate. The battery cell can include anelectrically conductive polymer tab to electrically connect theelectrode assembly to the second polarity terminal. The polymer tab canhave a first end and a second end. The first end of the polymer tab canbe electrically coupled with the vent plate at an area within the scoredregion defined by the scoring pattern on the vent plate. The second endof the polymer tab can be electrically coupled with the electrodeassembly. The polymer tab can melt in response to either a thresholdtemperature or a threshold current within the battery cell.

At least one aspect of this disclosure is directed to a method. Themethod can include providing a battery cell of a battery pack to poweran electric vehicle. The battery cell can include a housing to at leastpartially enclose an electrode assembly. The housing can define a sidesurface of the battery cell. The battery cell can include a firstpolarity terminal including at least a portion of the housing. Thebattery cell can include a vent plate coupled with the housing via aglass weld at a lateral end of the battery cell to electrically insulatethe vent plate from the housing. The vent plate can include a scoringpattern to cause the vent plate to rupture in response to a thresholdpressure within the battery cell. The scoring pattern can define ascored region on the vent plate. The battery cell can include a secondpolarity terminal including at least a portion of the vent plate. Thebattery cell can include an electrically conductive polymer tab toelectrically connect the electrode assembly to the second polarityterminal. The polymer tab can have a first end and a second end. Thefirst end of the polymer tab can be electrically coupled with the ventplate at an area within the scored region defined by the scoring patternon the vent plate. The second end of the polymer tab can be electricallycoupled with the electrode assembly. The polymer tab can melt inresponse to either a threshold temperature or a threshold current withinthe battery cell.

These and other aspects and implementations are discussed in detailbelow. The foregoing information and the following detailed descriptioninclude illustrative examples of various aspects and implementations,and provide an overview or framework for understanding the nature andcharacter of the claimed aspects and implementations. The drawingsprovide illustration and a further understanding of the various aspectsand implementations, and are incorporated in and constitute a part ofthis specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Likereference numbers and designations in the various drawings indicate likeelements. For purposes of clarity, not every component may be labeled inevery drawing. In the drawings:

FIG. 1 depicts a cross-sectional view of an example battery cell for anelectric vehicle battery pack;

FIG. 2 depicts a cross-sectional view of an example battery cell for anelectric vehicle battery pack;

FIG. 3 depicts an example vent plate and polymer tab for a battery cell;

FIG. 4 depicts an example vent plate and polymer tab for a battery cell;

FIG. 5 depicts a cross-sectional view of an example battery pack forholding battery cells in an electric vehicle;

FIG. 6 depicts a top-down view of an example battery pack for holdingfor battery cells in an electric vehicle;

FIG. 7 depicts a cross-sectional view of an example electric vehicleinstalled with a battery pack;

FIG. 8 depicts a flow chart of an example process undergone by a batteryexperiencing various conditions associated with thermal runaway;

FIG. 9 depicts a flow chart of an example process for manufacturing abattery cell for a battery pack of an electric vehicle; and

FIG. 10 depicts a flow chart of an example process of providing abattery cell for a battery pack of an electric vehicle.

Following below are more detailed descriptions of various conceptsrelated to, and implementations of, methods, apparatuses, and systems ofbattery cells for electric vehicles. The various concepts introducedabove and discussed in greater detail below may be implemented in any ofnumerous ways, as the described concepts are not limited to anyparticular manner of implementation.

DETAILED DESCRIPTION

Systems and methods described herein relate to battery cells for batterypacks (or battery modules) that can provide power to electric vehicles(“EVs”). Battery packs, which can be referred to herein as batterymodules, can include battery cells such as lithium ion battery cells.Such battery cells can perform well under normal operating conditions.However, certain abuse or out of tolerance range conditions can lead tothe failure of such battery cells. For example, when a battery cell isabused or subject to out of tolerance conditions thermally,electrically, or mechanically, the battery cell has the potential toundergo a condition known as thermal runaway. During thermal runaway,reactions occurring on the surface of an electrode or terminal of thebattery can cause heat generation, which in turn can accelerate the rateof the reaction, thereby creating a feedback loop that can result inrapid temperature acceleration of the battery. In some instances, thisfeedback loop can cause a battery cell failure.

Battery cell designs can incorporate aluminum current collectors bondedto the cathode and anode tabs attached to the electrodes. The cathode orpositive tab can bond to the lid assembly. The lid assembly can includesome form of current interrupt device (CID), gasket, and insulatingpolymer. Such assemblies can pose a technical problem, as multiple cellcomponents may be disposed in a crimped area of the battery cellhousing, thereby limiting the amount of space for the electrolyte orother active material within the housing. In addition, CID designs mayrespond to pressure, but may not respond to temperature or electricalstimuli. In extreme thermal events such as thermal runaway, anycombination of pressure, temperature, and current can spikeprecipitously.

FIG. 1 depicts an example battery cell 100 for an electric vehiclebattery pack. The battery cell 100 can includes one housing 105. Thehousing can include a head region 110, a neck region 115, and a bodyregion 120. The head region 110 can be positioned at a lateral end ofthe battery cell 100 that is opposite the body region 120. The bodyregion 120 of the housing 105 can contain an electrode assembly 125(e.g., a “jelly roll” 125) that provides electric power for the batterycell 100. The electrode assembly 125 can be or can include anelectrolyte material. For example, an electrolyte material, such as anionically conductive liquid, can penetrate the electrode assembly 125.At least a portion of the electrode assembly 125 can be electricallyconnected with a vent plate 130 of the battery cell 100, via at leastone connecting element 135. The vent plate 130 can therefore serve as afirst polarity terminal of the battery cell 100, and can also bereferred to in this disclosure as a first polarity terminal 130. Thevent plate 130 can be supported within the head region 110 by the neckregion 115 of the housing 105. A gasket 140 can surround the vent plate130 and can electrically insulate the vent plate 130 from the housing105. The gasket 140 can be formed from an electrically insulatingmaterial, such as a plastic or rubber material. For example, the gasket140 can be formed from polypropylene.

The housing 105 can be electrically insulated from a portion (e.g., apositively charged portion) of the electrode assembly 125 that iselectrically coupled with the vent plate 130 by the connecting element135. The housing 105 can also be electrically coupled to another portion(e.g., a negatively charged portion) of the electrode assembly 125 toallow the housing 105 to serve as a second polarity terminal of thebattery cell 100. For example, the housing 105 can be formed from aconductive metal, such as steel, aluminum, or copper, so that thehousing can conduct electrical current from a portion of the electrodeassembly 125. The top perimeter edge of the housing 105 can include alip 150, which can serve as the second polarity terminal and can beelectrically coupled to a negative portion of the electrode assembly 125contained within the housing 105. The lip 150 can also serve as asurface to which a wire can be bonded to carry current from the housing105 to a busbar or current collector.

Thermal runaway in the battery cell 100 can be preceded by an increasein any combination of gas pressure, temperature, or electric current inthe area beneath the vent plate 130 (e.g., a cap) of the battery cell100. The vent plate 130 can include a current interrupt device (CID) andone or more vents to release gas pressure buildup within the batterycell 100. For example, the vent plate 130 can include one or morescoring patterns 145 that allow the vent plate 130 to respond to aninternal pressure in the battery cell 100 by causing the vent plate 130to break, rupture, tear, or buckle away from the electrode assembly 125housed within the housing 105 when the pressure reaches or exceeds apressure threshold, thereby disconnecting or otherwise interrupting theflow of electric current and releasing the pressure. When pressurebuilds up beyond the pressure threshold, the vent plate 130 can rupturealong the scoring pattern 145, allowing gas to escape and relieving thepressure. The threshold pressure that causes the vent plate 130 torupture along the scoring pattern 145 can be between 60 pounds persquare inch (PSI) and 500 PSI.

The scoring pattern 145 can include one or more marks formed on or intoa surface of the vent plate 130. For example, the scoring pattern 145can include one or more troughs, divots, cutouts, holes, grooves,etches, or other patterns that render a thickness of the vent plate 130at the scoring pattern 145 thinner than a thickness of the unscoredportions of the vent plate 130. The scoring pattern 145 can be formed byremoving a portion of the material that makes up the vent plate 130, forexample by etching, scraping, ablating, vaporizing, or cutting away someof the material of the vent plate 130.

The scoring pattern 145 can be a continuous pattern, such as a groovethat is etched into a surface of the vent plate 130 to form a loop onthe surface of the vent plate 130. For example, the scoring pattern 145can be continuous and can enclose, define, or outline a scored region155 on a surface of the vent plate 130 in the shape of a circle, anoval, a rectangle, or any other curved or polygonal shape. In theexample cross-sectional view shown in FIG. 1, the triangular divotsrepresenting the scoring pattern 145 in the vent plate 130 can each bepositioned on opposite sides of such a loop. The scoring pattern 145also can be discontinuous. For example, the scoring pattern 145 caninclude a series of discontinuous troughs, divots, holes, grooves, orcutouts, such as a perforated line, that surrounds the scored region 155on the surface of the terminal 130. The scored region 155 defined by thescoring pattern 145 can be either a symmetrical pattern or anasymmetrical pattern. Generally, because the vent plate 130 is thinnerwhere the scoring pattern 145 is present than across a remainder (e.g.,an unscored portion) of the vent plate 130, the scoring pattern 145 cancause the vent plate 130 to tear or rupture along the scoring pattern145 in response to a threshold pressure within the battery cell 100. Thethreshold pressure can be predetermined. For example the vent plate 130or the scoring pattern 145 can be designed to rupture along at leastpart of the scoring pattern 145 responsive to pressure in excess of aspecified or rated amount. For example, the scoring pattern 145 can beselected to intentionally weaken the vent plate 130 along the scoringpattern 145 so that the vent plate 130 tears or ruptures when thethreshold pressure is reached inside the housing 105 (e.g., in the neckregion 115). Thus, when the threshold pressure is reached, the ventplate 130 can tear or rupture in a manner that separates the scoredregion 155 of the vent plate 130 defined by the scoring pattern 145, tobecome at least partially separated from a remainder of the vent plate130 (e.g., a portion of the vent plate 130 outside of the scored region155). As a result, gas that has built up and that causes pressure withinat least a portion of the battery cell 100 to meet or surpass thethreshold pressure can escape, thereby relieving the pressure within thebattery cell 100.

While the scoring pattern 145 on the vent plate 130 can allow the ventplate 130 to respond to pressure increases that may indicate thatthermal runaway is imminent or has already begun, the vent plate 130itself may not directly respond to other stimuli, such as electricalcurrent increases and temperature increases, that can also signal theonset of thermal runaway. The battery cell 100 and its variouscomponents described herein can provide solutions that can respond toboth of these stimuli (as well as to excessive gas pressure) to mitigatenegative consequences that can be caused by thermal events such asthermal runaway in the battery cell 100. For example, the battery cell100 described herein can incorporate the connecting element 135 to allowthe battery cell 100 to also respond to temperature and electricalcurrent at threshold levels to interrupt the flow of current within thebattery cell 100 when any one of those threshold levels is reached. Thethreshold levels for each of these stimuli can be selected based onlevels that may indicate that the onset of thermal runaway is imminentor that thermal runaway has already begun.

The connecting element 135 can also be referred to as a tab 135. The tab135 can electrically couple the electrode assembly 125 with the ventplate 130. The tab 135 can be formed from a conductive material. In someexamples, the tab 135 can be formed from a conductive metal or alloy,such as steel, aluminum, or copper. However, such metal materials mayhave a relatively high melting point, as well as relatively lowresistivity. As a result, such a material may not be impacted by hightemperatures or high electrical currents that can occur during thermalrunaway. A metal tab 135 may therefore continue to conduct electricityfrom the electrolyte 125 to the vent plate 130 even after anycombination of current or temperature levels has reached a thresholdvalue indicative of thermal runaway and out of tolerance for normaloperating conditions.

To address this technical challenge, the tab 135 can be formed from aconductive polymer material instead of from a metal or alloy. That is,the tab 135 can be a polymer tab and not a metal tab. The tab 135 can beformed from a polymer material that is conductive, thereby allowing thetab 135 to electrically couple the electrode assembly 125 with the ventplate 130. The polymer material of the tab 135 can also have a lowmelting point relative to a metal or alloy material, such as steel,aluminum, or copper. The polymer material of the tab 135 can also have ahigh resistivity relative to that of a metal or alloy. The low meltingpoint and high resistivity of the conductive polymer material selectedfor the tab 135 can achieve various technical benefits relating tointerrupting current in response to a thermal runaway condition, such asa threshold temperature or a threshold current. The tab 135 can have alength in the range of 10 millimeters to 20 millimeters and a width inthe range of 10 millimeters to 20 millimeters.

Forming the tab 135 from a conductive polymer material having a lowmelting point can allow the tab 135 to melt when a temperature insidethe battery cell 100 (e.g., a an ambient temperature in the neck region115 or the head region 110 of the housing 105) reaches the meltingtemperature of the conductive polymer. In some examples, the polymermaterial of the tab 135 can be selected to have a melting point at ornear a threshold temperature that precedes or coincides with thermalrunaway. A threshold temperature associated with thermal runaway can bein the range of 120 degrees C. to 140 degrees C., and the polymermaterial selected for the tab 135 can be selected to have a meltingpoint in this range. For example, the threshold temperature (and themelting point of the polymer material used to form the tab 135) may be130 degrees C. Thus, when the threshold temperature is reached, the tab135 can melt, thereby severing the connection that electrically couplesthe electrode assembly 125 with the vent plate 130 to stop the flow ofelectricity in the battery cell 100. In contrast, conductive metals andalloys may have substantially higher melting points, such as 550 degreesC. to 650 degrees C., and may therefore not be able to melt in responseto a threshold temperature in the range of 120 degrees C. to 140 degreesC.

The polymer material of the tab 135 can also be selected to have arelatively high resistivity, compared to the resistivity of a metal oralloy. High resistivity can lead to resistive heating when highelectrical currents pass through the tab 135. The polymer material ofthe tab 135 can be selected such that the tab 135 heats to a temperatureat or above its melting point when a threshold current passes throughthe tab 135. Thus, the tab 135 can melt when the threshold current isreached, thereby severing the electrical connection between theelectrode assembly 125 and the terminal 130 to interrupt the flow ofcurrent in the battery cell 100. The threshold current can be a currentthat indicates a thermal runaway event is imminent or has already begun.For example, the threshold current that triggers melting of the tab 135can be in the range of 50 A to 100 A. When the threshold current isreached, the tab 135 can melt. Thus, the tab 135 can act as a fuse toprohibit the flow of current when a threshold current level is reached.In some examples, the polymer material used for the tab 135 can includepolyacetylene, polyphenylene vinylene, or polypyrrole. In some examples,the polymer material used for the tab 135 may be a highly crystallinematerial doped with conductive additives.

FIG. 2 depicts a cross-sectional view 200 of an example battery cell 100for an electric vehicle battery pack. The battery cell 100 can includeat least one housing 105, which can enclose an electrolyte 125. Thebattery cell 100 can also include at least one vent plate 130. The ventplate 130 can be electrically coupled with the electrolyte 125 via a tab135. The vent plate 130 can include a scoring pattern 145 that canenclose or define a scored region 155.

The housing 105 in some examples is not crimped to define any separatebody region, neck region, or head region. Instead, the housing 105includes an uncrimped sidewall 205 (which can also be referred to inthis disclosure as a side surface 205). The uncrimped sidewall 205 canextend straight along a lateral direction of the battery cell 100, andis not bent, crimped, deformed, or otherwise shaped in a manner thatdefines a body region, a neck region, or a head region as shown inFIG. 1. Because there is no neck region or other crimped portion of thehousing 105 configured to support the vent plate 130, the vent plate 130can be supported in a different manner. For example, in FIG. 2, the ventplate 130 can be secured to the housing 105 via a weld 210. The weld 210can be, for example a glass weld. In other examples, the weld 210 can bea different type of weld. Generally, the weld 210 can secure the ventplate 130 to the housing 105 and to hold the vent plate 130 in position.The weld 210 can also electrically insulate the vent plate 130 from thehousing 105. Therefore, the weld 210 can be formed from an insulatingmaterial, such as glass.

Because the vent plate 130 is held in place, and electrically insulatedfrom the housing 105 in some examples by the weld 210, the battery cell100 may not include any gasket. In addition, while the vent plate 130can include, house, or accommodate a positive temperature coefficient(PTC) polymer to provide thermal protection, the battery cell 100 caninclude the polymer tab 135 and may not include any additional PTCpolymer in the vent plate 130. In this example, the battery cell 100with the polymer tab 135 and without a PTC polymer positioned in thevent plate can include one less component (as there is no PTC polymer inthe vent plate 130) than a design including such a PTC polymer. Inexamples in which a PTC polymer may be included in the vent plate 130,the resistance of the PTC polymer can increase rapidly as temperatureincreases, cutting off the current within the battery cell 100.

Because the housing 105 in some examples is not bent or crimped todefine any separate body region, neck region, or head region, there canbe more space available inside the housing 105 for enclosing theelectrode assembly 125. As a result, there can be more electrodeassembly 125 housed within the battery cell 100 of FIG. 2 as compared tothe amount of electrode assembly 125 housed within the battery cell 100of FIG. 1, thereby leading to a greater energy density for the batterycell 100 in some examples. For example, the housing 105 of FIG. 1 mayinitially be formed with a straight sidewall, such that the housing 105has a cylindrical shape. The cylindrical housing 105 can be bent ordeformed through one or more crimping operations to define the headregion 110, the neck region 115, and the body region 120. The one ormore crimping operations can therefore reduce the overall height of thebattery cell 100. This can cause the electrode assembly 125 to bepositioned nearer to the vent plate 130 than in a crimped configuration,as no vertical space is required for the neck region that may be presentin the crimped configuration. For example, the electrode assembly 125can be positioned within 0.2 millimeters to 8 millimeters of the ventplate 130 in the example of FIG. 2.

By reducing or eliminating the need for any crimping operations throughuse of the weld 210, the battery cell 100 can have an increased height(and therefore an increased volume for housing the electrode assembly125) relative to a crimped battery cell 100. In some examples, theheight of the battery cell 100 of FIG. 2 (e.g., the length of thesidewall 205) can be between 65 millimeters and 75 millimeters. Bybypassing the crimping operation, the length in the housing 105available to the electrode assembly 125 can increase from, for example,65 mm to 67 mm. Other shapes, sizes, and dimensions are possible for thebattery cell 100 and for the electrode assembly 125 housed therein. Thehousing 105 can have a diameter between 24 millimeters and 28millimeters. The housing 105 can also have a diameter in the range of 19millimeters to 23 millimeters. The vent plate 130 can have a diameterless than that of the housing 105 to allow the vent plate 130 to fitinto the housing 105 and to be secured to the housing 105 via the weld210.

FIG. 3 depicts a perspective view 300 of an example vent plate 130 andpolymer tab 135 for a battery cell. Also shown is the electrode assembly125. FIG. 3 shows the vent plate 130 and the tab 135 in a configurationthat can result from any combination of a threshold temperature or athreshold current being reached. As depicted, such a condition can causethe tab 135 to become severed at the area labeled 305, therebyelectrically disconnecting the electrode assembly 125 from the ventplate 130. A wire 310 can couple the vent plate 130 to a currentcollector 315, which can also be referred to as a busbar 315.

The tab 135 has a first end coupled to the vent plate 130, and a secondend coupled to the electrode assembly 125. Generally, the tab 135 can becoupled, joined, or otherwise fastened to the vent plate 130 and theelectrode assembly 125 in any manner that allows the tab 135 to form anelectrical connection with each of the vent plate 130 and the tab 135.For example, the tab 135 can be coupled to the vent plate 130 or theelectrode assembly 125 via an electrically conductive adhesive or one ormore electrically conductive mechanical fasteners. The tab 135 can alsobe coupled to the vent plate 130 or the electrode assembly 125 via apress fit or friction fit.

When a high temperature (e.g., a temperature meeting or exceeding amelting point of the tab 135) is experienced, the tab 135 can at leastpartially melt, open, or tear until it becomes severed at the point 305.The position of the point 305 along the length of the tab 135 is anexample. Melting of the tab 135 in response to the threshold temperaturecan cause the tab 135 to become severed at any point along its length,or at multiple points along its length, such that the electricalconnection initially formed between the electrode assembly 125 and thevent plate 130 is broken. As a result, electrical current will no longerflow via the tab 135 between the electrode assembly 125 and the ventplate 130. Therefore, current can no longer be delivered from theelectrode assembly 125 to the current collector 315 via the wire 310.The melting point of the tab 135 can be selected to coincide with or beclose to (e.g., 1-40% less than) a threshold temperature that indicatesa thermal runaway condition. In some examples, the material selected forthe tab 135 can be a polymer material having such a melting point, whichmay be lower than the melting point of conductive metals or alloys. Forexample, the melting point of the polymer material selected for the tab135 can be in the range of 120 degrees C. to 140 degrees C.

When a threshold current (e.g., an electrical current passing throughthe tab 135) is reached, the tab 135 may similarly melt until it becomessevered at the point 305. For example, high current can cause thetemperature of the tab 135 to increase due to resistive heating. Thematerial selected for the tab 135 can be a polymer material selected toheat to at least its melting point in response to the threshold current.As a result, the tab 135 can melt when the threshold current is reached,thereby interrupting or cutting off the flow of electrical currentbetween the vent plate 130 and the electrode assembly 125. Therefore,current can no longer be delivered from the electrode assembly 125 tothe current collector 315 via the wire 310. The position of the point305 along the length of the tab 135 is only one example. In some otherexamples, melting of the tab 135 in response to the threshold currentcan cause the tab 135 to become severed at any point along its length,or at multiple points along its length, such that the electricalconnection initially formed between the electrode assembly 125 and thevent plate 130 is broken.

FIG. 4 depicts a perspective view 400 of an example vent plate 130 andpolymer tab 135 for a battery cell. For illustrative purposes, othercomponents of the battery cell 100 are not depicted in FIG. 4. FIG. 4shows the vent plate 130 and the tab 135 in a configuration that canresult from a threshold pressure being reached. As depicted, such acondition can cause the scored region 155 of the vent plate 130 tobecome severed from a remainder (e.g., an unscored portion) of the ventplate 130, thereby electrically disconnecting the electrode assembly 125from the remainder of the vent plate 130.

The tab 135 has a first end coupled to the vent plate 130, and a secondend coupled to the electrode assembly 125. In some examples, the tab 135can be coupled to the vent plate 130 at any point within the scoredregion 155. The scored region 155 is shown as being generally circularin shape, however other shapes are also possible. The wire 310 can becoupled to the vent plate 130 at any point outside of the scored region155. A second end of the tab 135 can be coupled to the electrodeassembly 125.

As pressure increases, stresses can accumulate in the vent plate 130.Due to the scoring pattern 145 formed on the surface of the vent plate130, the vent plate 130 can rupture or tear along the scoring pattern145 when a threshold pressure is reached. As a result, the scored region155 of the vent plate 130 can become separated from a remainder of thevent plate 130, as depicted in FIG. 4. For example, the thresholdpressure can cause the scored region 155 of the vent plate 130 to beforced up and away from a remainder of the vent plate 130, because theremainder of the vent plate 130 can be secured in place by either thecrimping of a neck region 115 of the housing 105, as depicted in FIG. 1,or by a weld 210 that secures the remainder of the vent plate 130 to thehousing 105, as depicted in FIG. 2. When the scored region 155 of thevent plate 130 is forced away from the remainder of the vent plate 130,the tab 135 can become severed or torn at the point labeled 405. FIG. 4depicts the point 405 as being near the electrode assembly 125, howeverother locations are possible. For example, the tab 135 can insteadbecome severed or torn at a point nearer to the vent plate 130, or atmultiple points along the length of the tab 135.

In some examples, the tab 135 may instead remain intact even after thescored region 155 of the vent plate 130 becomes separated from theremainder of the vent plate 130. However, even if the tab 135 remainsintact, electrical current can still be interrupted. For example, bysecuring the tab 135 to the vent plate 130 at a point within the scoredregion 155 of the vent plate 130, and securing the wire 310 to the ventplate 130 at a point outside of the scored region 155, an electricalconnection between the wire 310 and the electrode assembly 125 issevered when the scored region 155 of the vent plate 130 tears,ruptures, or otherwise becomes separated from the remainder of the ventplate 130. Thus, even in examples in which the tab 135 may remainintact, the threshold pressure can still cause the vent plate 130 totear in a manner that prevents electrical current from being deliveredto the current collector 315.

FIG. 5 depicts a cross-section view 500 of a battery pack 505 to hold aplurality of battery cells 100 in an electric vehicle. The battery pack505 can include a battery module case 510 and a capping element 515. Thebattery module case 510 can be separated from the capping element 515.The battery module case 510 can include or define a plurality of holders520. Each holder 520 can include a hollowing or a hollow portion definedby the battery module case 510. Each holder 520 can house, contain,store, or hold a battery cell 100. The battery module case 510 caninclude at least one electrically or thermally conductive material, orcombinations thereof. The battery module case 510 can include one ormore thermoelectric heat pumps. Each thermoelectric heat pump can bethermally coupled directly or indirectly to a battery cell 100 housed inthe holder 520. Each thermoelectric heat pump can regulate temperatureor heat radiating from the battery cell 100 housed in the holder 520.Bonding elements 550 and 555, which can each be electrically coupledwith a respective terminal (e.g., a portion of the housing 105 or thevent plate 130) of the battery cell 100, can extend from the batterycell 100 through the respective holder 520 of the battery module case510.

Between the battery module case 510 and the capping element 515, thebattery pack 505 can include a first busbar 525, a second busbar 530,and an electrically insulating layer 535. The first busbar 525 and thesecond busbar 530 can each include an electrically conductive materialto provide electrical power to other electrical components in theelectric vehicle. The first busbar 525 (sometimes referred to as a firstcurrent collector) can be connected or otherwise electrically coupledwith the first bonding element 550 extending from each battery cell 100housed in the plurality of holders 520 via a bonding element 545. Thebonding element 545 can be bonded, welded, connected, attached, orotherwise electrically coupled with the bonding element 550. Forexample, the bonding element 545 can be welded onto a top surface of thebonding element 550. The second busbar 530 (sometimes referred to as asecond current collector) can be connected or otherwise electricallycoupled with the second bonding element 555 extending from each batterycell 100 housed in the plurality of holders 520 via a bonding element540. The bonding element 540 can be bonded, welded, connected, attached,or otherwise electrically coupled with the second bonding element 555.For example, the bonding element 540 can be welded onto a top surface ofthe second bonding element 555. The second busbar 530 can define thesecond polarity terminal for the battery pack 505. Each the busbar 525or the busbar 530 may serve as a current collector similar to thecurrent collector 315.

The first busbar 525 and the second busbar 530 can be separated fromeach other by the electrically insulating layer 535. The electricallyinsulating layer 535 can include spacing to pass or fit the firstbonding element 550 connected to the first busbar 525 and the secondbonding element 555 connected to the second busbar 530. The electricallyinsulating layer 535 can partially or fully span the volume defined bythe battery module case 510 and the capping element 515. A top plane ofthe electrically insulating layer 535 can be in contact or be flush witha bottom plane of the capping element 515. A bottom plane of theelectrically insulating layer 535 can be in contact or be flush with atop plane of the battery module case 510. The electrically insulatinglayer 535 can include any electrically insulating material or dielectricmaterial, such as air, nitrogen, sulfur hexafluoride (SF₆), porcelain,glass, and plastic (e.g., polysiloxane), among others to separate thefirst busbar 525 from the second busbar 530.

FIG. 6 depicts is a top-down view 600 of a battery pack 505 to hold aplurality of battery cells 100 in an electric vehicle. The battery pack505 can define or include a plurality of holders 520. The shape of eachholder 520 can be triangular, rectangular, pentagonal, elliptical, andcircular, among others. The shapes of each holder 520 can vary or can beuniform throughout the battery pack 505. For example, some holders 520can be hexagonal in shape, whereas other holders can be circular inshape. The shape of the holder 520 can match the shape of a housing ofeach battery cell 100 contained therein. The dimensions of each holder520 can be larger than the dimensions of the battery cell 100 housedtherein.

FIG. 7 depicts is a cross-section view 700 of an electric vehicle 705installed with a battery pack 505. The electric vehicle 705 can includea chassis 710 (e.g., a frame, internal frame, or support structure). Thechassis 710 can support various components of the electric vehicle 705.The chassis 710 can span a front portion 715 (e.g., a hood or bonnetportion), a body portion 720, and a rear portion 725 (e.g., a trunkportion) of the electric vehicle 705. The battery pack 505 can beinstalled or placed within the electric vehicle 705. The battery pack505 can be installed on the chassis 710 of the electric vehicle 705within the front portion 715, the body portion 720 (as depicted in FIG.7), or the rear portion 725. The first busbar 525 and the second busbar530 can be connected or otherwise be electrically coupled with otherelectrical components of the electric vehicle 705 to provide electricalpower. The battery cells 100 can each include a vent plate 130 and apolymer tab 135 in order to respond to any combination of a thresholdpressure, a threshold temperature, and a threshold current in the mannerdescribed above.

FIG. 8 depicts an example process 800 of battery cells 100 operationsfor battery packs of electric vehicles. The battery cells 100 caninclude the vent plate 130 and the tab 135 that can respond to thresholdconditions of pressure, temperature, and current, each of which may beindicative of an imminent or ongoing thermal runaway condition for thebattery cell 100. The process 800 depicts example conditions associatedwith thermal runaway. The process 800 begins at block 805, in which thebattery cell 100 is operating, for example under normal conditions. Inthe event of a threshold temperature being reached within the batterycell 100, the process 800 can proceed to block 810. The thresholdtemperature can be any temperature known to indicate the onset of athermal runaway event for the battery cell 100. The process 800 canproceed to block 825, in which the tab 135 melts in response to thethreshold temperature being reached. For example, the vent plate 130 canbe formed from a polymer material having a melting point thatcorresponds to the threshold temperature reached in block 810. Becausethe tab 135 forms part of the current path from the electrode assembly125 to the vent plate 130, which can serve as a first polarity terminalof the battery cell 100, melting of the tab 135 interrupts the currentpath and arrests this current, as indicated in block 840 of the process800.

Referring again to block 805, when a threshold pressure is reached inthe battery cell 100, the process 800 can proceed to block 815. Thethreshold pressure can be any pressure that indicates the onset of athermal runaway event for the battery cell 100. The process 800 canproceed to block 830, in which the vent plate 130 tears or ruptures. Forexample, the vent plate 130 can include a scoring pattern 145surrounding a scored region 155 and designed to cause the vent plate 130to rupture along the scoring pattern 145 when the threshold pressure isreached. This tearing or rupturing can cause the scored region 155 ofthe vent plate 130 to become separated from a remainder of the ventplate 130. As a result, the current path in the battery cell 100 can bebroken.

Again referring to block 805, when a threshold current is reached in thebattery cell 100, the process 800 can proceed to block 820. Thethreshold current can be any current that indicates the onset of athermal runaway event for the battery cell 100. The process 800 canproceed to block 835, in which the tab 135 melts. For example, the highcurrent can heat the tab 135 rapidly through resistive heating effects,eventually exceeding its melting temperature. The tab 135 can thereforemelt in response to the high current, serving as a fuse to interrupt thecurrent path through the battery cell 100. As a result, the current canbe interrupted, as indicated in block 840 of the process 800.

FIG. 9 depicts a flow chart of an example process 900 for manufacturinga battery cell 100 for a battery pack of an electric vehicle. The method900 can include forming a housing 105 for the battery cell 100 (ACT905). The housing 105 can define a sidewall 205 or side surface 205 ofthe battery cell 100. The housing 105 can form at least a portion of afirst polarity terminal of the battery cell 100. In some examples, thehousing 105 can be cylindrical in shape, and the side surface 205 maynot include any crimped region. For example, the sidewall 205 can extendstraight between opposing ends of the housing 105, and may not be bent,deformed, or crimped to define any separate head, neck, or body portionsof the housing 105. The method 900 can also include providing anelectrode assembly 125 within the housing 105 (ACT 910). The electrodeassembly 125 can include any electrically active material capable ofsupplying electric power for the battery cell 100.

The method 900 can include etching a scoring pattern 145 into a ventplate 130 (ACT 915). The scoring pattern 145 can be any type of patternconfigured or selected to cause the vent plate 130 to rupture whenexposed to a pressure that exceeds a predetermined or other thresholdpressure. For example, the scoring pattern 145 can intentionally weakena portion of the vent plate 130. The etching of the scoring pattern canbe achieved by any suitable means, such as by using a mechanical cuttingtool (e.g., a blade) or a laser to etch, ablate, or otherwise remove aportion of the material on a surface of the vent plate 130 to define thescoring pattern 145. The scoring pattern 145 can define or enclose ascored region 155 on the vent plate 130. The vent plate 130 can form atleast a portion of a second polarity terminal of the battery cell 100.

The method 900 can include electrically coupling a first end of anelectrically conductive polymer tab 135 with the vent plate 130 (ACT920). The tab 135 can be coupled with the vent plate 130 at an areawithin the scored region 155 defined by the scoring pattern 145 on thevent plate 130. The polymer tab 135 can be coupled to the vent plate130, for example, by an electrically conductive adhesive, anelectrically conductive mechanical fastener, or by a press fit orfriction fit. The polymer tab 135 can be formed from a material selectedto melt when exposed to either a threshold temperature or a thresholdcurrent. The threshold temperature or current can be predetermined. Forexample the polymer tab 135 can be designed to melt, tear, or openresponsive to temperature or current in applied to the polymer tab 135exceeding a specified or rated amount. For example, the materialselected for the polymer tab 135 can have a melting point at or near thethreshold temperature. The material selected for the polymer tab 135 canalso have a resistivity that causes the tab 135 to heat to a temperatureat or above its melting point in response to the threshold current. Insome examples, the threshold temperature can be in the range of 120degrees C. to 140 degrees C., and the threshold current can be in therange of 50 A to 100 A.

The method 900 can include electrically coupling a second end of thepolymer tab 135, opposite the first end of the polymer tab 135, with theelectrode assembly 125 (ACT 925). The polymer tab 135 can be coupled tothe electrode assembly 125, for example, by an electrically conductiveadhesive, an electrically conductive mechanical fastener, or by a pressfit or friction fit. The method 900 can also include coupling the ventplate 130 with housing 105 (ACT 930). The vent plate 130 can be coupledwith the housing 105, for example, via a glass weld 210. The glass weld210 can secure the vent plate 130 to the housing 105. The glass weld 210can also electrically insulate the vent plate 130 from the housing 105,and can form a seal around the electrode assembly 125 and the polymertab 135. In some examples, using the glass weld 210 to secure the ventplate 130 to the housing 105 may dispense with any need for using agasket to electrically insulate the vent plate 130 from the housing 105,and may also dispense with any need to form a crimped area in thehousing 105 to support the vent plate 130. Thus, in some examples, themethod 900 may not include positioning a gasket in the housing 105. Themethod 900 also may not include performing a crimping operation on thehousing 105.

FIG. 10 depicts a flow chart of an example process 1000. The process1000 can include providing a battery cell 100 (ACT 1005). The batterycell 100 can be a battery cell 100 for an electric vehicle battery pack.The battery cell 100 can include a housing 105 to at least partiallyenclose an electrode assembly 125. The housing 105 can define a sidesurface of the battery cell 100. The battery cell 100 can include afirst polarity terminal including at least a portion of the housing 105.The battery cell can include a vent plate 130 coupled with the housing105 via a glass weld 210 at a lateral end of the battery cell 100 toelectrically insulate the vent plate 130 from the housing 105. The ventplate 130 can include a scoring pattern 145 to cause the vent plate 130to rupture in response to a threshold pressure within the battery cell100. The scoring pattern 145 can define a scored region 155 on the ventplate 130. The battery cell 100 can include a second polarity terminalincluding at least a portion of the vent plate 130. The battery cell 100can include an electrically conductive polymer tab 135 to electricallyconnect the electrode assembly 125 to the second polarity terminal. Thepolymer tab 135 can have a first end and a second end. The first end ofthe polymer tab 135 can be electrically coupled with the vent plate 130at an area within the scored region 155 defined by the scoring pattern145 on the vent plate 130. The second end of the polymer tab 135 can beelectrically coupled with the electrode assembly 125. The polymer tab135 can melt in response to either a threshold temperature or athreshold current within the battery cell 100.

The solution described in this disclosure provides multiple technicaladvantages. For example, while battery cell designs having aluminumcathode and anode tabs may have a higher melting point (e.g., 600 C)than the polymer tab 135. The lower melting point relative to analuminum tab or other metal or alloy tab provides tab-based protectionagainst excessive temperature and also a higher resistivity thanaluminum or other metals, which can allow the polymer tab 135 to act asa fuse. In addition to this advantage, the lack of a crimp and the userof a glass welding technique can offer space advantages so that a largervolume of electrode assembly 125 can be stored within the battery cell100.

The crimp-free design with glass welding 210 to the vent plate 130 andthe use of the polymer tab 135 can better protect against thresholdcurrents and threshold temperatures associated with thermal runaway,relative to designs that incorporate a crimp, use an aluminum tab, orthat forego glass welding between the vent plate 130 and the housing105.

Having now described some illustrative implementations, it is apparentthat the foregoing is illustrative and not limiting, having beenpresented by way of example. Features that are described herein in thecontext of separate implementations can also be implemented incombination in a single embodiment or implementation. Features that aredescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in varioussub-combinations. References to implementations or elements or acts ofthe systems and methods herein referred to in the singular may alsoembrace implementations including a plurality of these elements, and anyreferences in plural to any implementation or element or act herein mayalso embrace implementations including only a single element. Referencesin the singular or plural form are not intended to limit the presentlydisclosed systems or methods, their components, acts, or elements tosingle or plural configurations. References to any act or element beingbased on any act or element may include implementations where the act orelement is based at least in part on any act or element.

References to “or” may be construed as inclusive so that any termsdescribed using “or” may indicate any of a single, more than one, andall of the described terms. References to at least one of a conjunctivelist of terms may be construed as an inclusive OR to indicate any of asingle, more than one, and all of the described terms. For example, areference to “at least one of ‘A’ and ‘B’” can include only ‘A’, only‘B’, as well as both ‘A’ and ‘B’. Such references used in conjunctionwith “comprising” or other open terminology can include additionalitems.

Where technical features in the drawings, detailed description or anyclaim are followed by reference signs, the reference signs have beenincluded for the sole purpose of increasing the intelligibility of thedrawings, detailed description, and claims. Accordingly, neither thereference signs nor their absence have any limiting effect on the scopeof any claim elements.

The systems and methods described herein may be embodied in otherspecific forms without departing from the characteristics thereof. Forexample, descriptions of positive and negative electricalcharacteristics may be reversed. For example, elements described asnegative elements can instead be configured as positive elements andelements described as positive elements can instead by configured asnegative elements. Further relative parallel, perpendicular, vertical orother positioning or orientation descriptions include variations within+/−10% or +/−10 degrees of pure vertical, parallel or perpendicularpositioning. References to “approximately,” “substantially” or otherterms of degree include variations of +/−10% from the given measurement,unit, or range unless explicitly indicated otherwise. Coupled elementscan be electrically, mechanically, or physically coupled with oneanother directly or with intervening elements. Scope of the systems andmethods described herein is thus indicated by the appended claims,rather than the foregoing description, and changes that come within themeaning and range of equivalency of the claims are embraced therein.

What is claimed is:
 1. A battery cell of a battery pack to power anelectric vehicle, comprising: a housing to at least partially enclose anelectrode assembly, the housing defining a side surface of the batterycell; a first polarity terminal comprising at least a portion of thehousing; a vent plate coupled with the housing via a glass weld at alateral end of the battery cell to electrically insulate the vent platefrom the housing, the vent plate including a scoring pattern to causethe vent plate to rupture in response to a threshold pressure within thebattery cell, the scoring pattern defining a scored region on the ventplate; a second polarity terminal comprising at least a portion of thevent plate; and an electrically conductive polymer tab to electricallyconnect the electrode assembly to the second polarity terminal, thepolymer tab having a first end and a second end, the first end of thepolymer tab electrically coupled with the vent plate at an area withinthe scored region defined by the scoring pattern on the vent plate, thesecond end of the polymer tab electrically coupled with the electrodeassembly, the polymer tab to melt in response to at least one of athreshold temperature and a threshold current within the battery cell.2. The battery cell of claim 1, wherein the threshold temperature is ina range of 120 degrees Celsius to 140 degrees Celsius.
 3. The batterycell of claim 1, wherein the threshold current is in a range of 50 A to100 A.
 4. The battery cell of claim 1, wherein the threshold pressure isin a range of 60 PSI to 500 PSI.
 5. The battery cell of claim 1,comprising: The polymer tab having a width in a range of 10 millimetersto 20 millimeters.
 6. The battery cell of claim 1, wherein: the glassweld forms a seal to separate the electrode assembly from an externalenvironment outside of the battery cell.
 7. The battery cell of claim 1,wherein: the housing is not crimped around the vent plate.
 8. Thebattery cell of claim 1, comprising: the scoring pattern including acontinuous line that forms a loop surrounding the scored region on thevent plate.
 9. The battery cell of claim 1, comprising: the scoringpattern including a perforated line that surrounds the scored region onthe vent plate.
 10. The battery cell of claim 1, comprising: the housinghaving a diameter in a range of 19 millimeters to 23 millimeters; andthe vent plate having a diameter less than the diameter of the housing.11. The battery cell of claim 1, comprising: the housing having a heightin a range of 65 millimeters to 75 millimeters.
 12. The battery cell ofclaim 1, comprising: the electrode assembly separated from the ventplate by a distance between 0.2 millimeters and 8 millimeters.
 13. Thebattery cell of claim 1, comprising: the polymer tab formed from atleast one of polyacetylene, polyphenylene vinylene, and polypyrrole. 14.The battery cell of claim 1, comprising: the battery cell included in abattery pack that includes a plurality of additional battery cells. 15.The battery cell of claim 1, comprising: the battery cell disposed in anelectric vehicle.
 16. A method of providing battery cells for batterypacks of electric vehicles, comprising: forming a housing for a batterycell of a battery pack having a plurality of battery cells, the housingdefining a side surface of the battery cell, the housing forming atleast a portion of a first polarity terminal of the battery cell;providing an electrode assembly within the housing; etching a scoringpattern into a vent plate to cause the vent plate to rupture whenexposed to a pressure exceeding a threshold pressure, the scoringpattern defining a scored region on the vent plate, the vent plateforming at least a portion of a second polarity terminal of the batterycell; electrically coupling a first end of an electrically conductivepolymer tab with the vent plate at an area within the scored regiondefined by the scoring pattern on the vent plate, the polymer tab tomelt when exposed to at least one of a threshold temperature and athreshold current; electrically coupling a second end of the polymertab, opposite the first end of the polymer tab, with the electrodeassembly; and coupling the vent plate with housing via a glass weld toform a seal around the electrode assembly and the polymer tab.
 17. Themethod of claim 16, comprising: etching the scoring pattern into thevent plate by etching a continuous line that forms a loop surroundingthe scored region on the vent plate.
 18. The method of claim 16,comprising: etching the scoring pattern into the vent plate by etching aperforated line that surrounds the scored region on the vent plate. 19.The method of claim 16, wherein: providing the battery cell, wherein thehousing for a battery cell is not crimped around the vent plate.
 20. Anelectric vehicle, comprising: a battery pack installed in the electricvehicle; and a battery cell in the battery pack, comprising: a housingto at least partially enclose an electrode assembly, the housingdefining a side surface of the battery cell; a first polarity terminalcomprising at least a portion of the housing; a vent plate coupled withthe housing via a glass weld at a lateral end of the battery cell toelectrically insulate the vent plate from the housing, the vent plateincluding a scoring pattern to cause the vent plate to rupture inresponse to a threshold pressure within the battery cell, the scoringpattern defining a scored region on the vent plate; a second polarityterminal comprising at least a portion of the vent plate; and anelectrically conductive polymer tab to electrically connect theelectrode assembly to the second polarity terminal, the polymer tabhaving a first end and a second end, the first end of the polymer tabelectrically coupled with the vent plate at an area within the scoredregion defined by the scoring pattern on the vent plate, the second endof the polymer tab electrically coupled with the electrode assembly, thepolymer tab to melt in response to at least one of a thresholdtemperature and a threshold current within the battery cell.